A paper entitled "The Study of the Analysis of Laser Stimulated Fluorescence Spectrum of the Digestive System and the Nature of it's Fluorescent Material," relating to the use of an argon laser having a wavelength of 5145 A as a light source has appeared in the Journal of the Japanese Association for Digestive Organ Endoscopy, Vol. 26, 8 Aug. 1984. The paper, more particularly, demonstrates the use of such an argon laser as a light source for directly illuminating an isolated specimen from the body and analyzing the intrinsic fluorescence spectrum generated by the light source to determine whether a malignant tumor exists in the isolated specimen. It has been found, however, that the method cannot be used satisfactory to diagnose gastric cancer, and its accuracy in the diagnosis of cancer of the large intestine was found to be only 30%. This is because the blue-green light of the argon-ion laser is visible light that superimpose upon the visible light waveband of the fluorescence spectrum generated by its stimulation on the isolated speciment, which is liable to lead to erroneous diagnosis. Moreover, the research studies embodied in this paper are only in the stage of experimentation, and up to this time no complete apparatus has achieved a satisfactory diagnosis of a malignant tumor.